Solve the simultaneous equations x + y = 13 and 2x + y = 22. What is the value of x?

Answer and explanation

Correct answer: A. 9

  1. Step 1: Subtract the first equation from the second: (2x + y) - (x + y) = 22 - 13, so x = 9. Step 2. Check in the first equation: y = 13 - 9 = 4, and 2(9) + 4 = 22. Answer: 9. Why not the others: 4: That is the value of y, found from x + y = 13. 10: Subtracting the two equations gives x exactly; one more does not satisfy both equations. 8: Subtracting the two equations gives x exactly; one less does not satisfy both equations.

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